Sputtering targets formed from cast materials

ABSTRACT

Described is a high quality sputtering target and method of manufacture which involves application of equal channel angular extrusion.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is related to application Ser. No. 09/098,761, filedJun. 17, 1998.

BACKGROUND OF THE INVENTION

The invention relates to sputtering targets and methods of making same;and to sputtering targets of high purity metals and alloys. Among thesemetals are Al, Ti, Cu, Ta, Ni, Mo, Au, Ag, Pt and alloys thereof,including alloys with these and or other elements. Sputtering targetsmay be used in electronics and semiconductor industries for depositionof thin films. To provide high resolution of thin films, uniform andstep coverages, effective sputtering rate and other requirements,targets should have homogenous composition, fine and uniform instructure, controllable texture and be free from precipitates, particlesand other inclusions. Also, they should have high strength and simplerecycling. Therefore, significant improvements are desired in themetallurgy of targets especially of large size targets.

A special deformation technique known as equal channel angular extrusion(ECAE) described in U.S. Pat. Nos. 5,400,633; 5,513,512; 5,600,989; andPat. No. 5,590,389 is used with advantage in accordance with theinvention. The disclosures of the aforementioned patents are expresslyincorporated herein by reference.

SUMMARY OF THE INVENTION

The invention relates to a sputtering target made by a process includingcasting. The target has a target surface such that the surface of thetarget subjected to sputtering (referred to as target surface) has asubstantially homogeneous composition at any location, substantialabsence of pores, voids, inclusions and other casting defects, grainsize less than about 1 μum and substantially uniform structure andtexture at any location. Preferably, the target comprises at least oneof Al, Ti, Cu, Ta, Ni, Mo, Au, Ag, Pt and alloys thereof.

The invention also relates to a method of manufacturing a target, asdescribed above. The method comprises fabricating an article-suitablefor use as a sputtering target comprising the steps of:

-   -   a. providing a cast ingot;    -   b. homogenizing said ingot at time and temperature sufficient        for redistribution of macrosegregations and microsegregations;        and    -   c. subjecting said ingot to equal channel angular extrusion to        refine grains therein.

More particularly, a method of making a sputtering target comprising thesteps of:

-   -   a. providing a cast ingot with a length-to-diameter ratio up to        2;    -   b. hot forging said ingot with reductions and to a thickness        sufficient for healing and full elimination of case defects;    -   c. subjecting said hot forged product to equal channel        extrusion; and    -   d. manufacturing into a sputtering target.

Still-more particularly, a method of fabricating an article suitable foruse as a sputtering target comprising the steps of:

-   -   a. providing a cast ingot;    -   b. solutionizing heat treating said cast ingot at temperature        and time necessary to dissolve all precipitates and particle        bearing phases; and    -   c. Equal channel angular extruding at temperature below aging        temperatures.

After fabricating as described to produce an article, it may bemanufactured into a sputtering target.

DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1D are schematic diagrams showing processing steps of billetpreparation for ECAE;

FIG. 2 is a graph showing the effect of annealing temperature on billetstrength after 4 and 6 passes of ECAE for Al 0.5 wt. % Cu alloy;

FIG. 3A is a schematic diagram disclosing an apparatus for gradientannealing of targets;

FIG. 3B is a schematic diagram showing temperature distribution throughtarget cross-section C—C during gradient annealing;

FIG. 4 is an illustration of (200) pole figures for Al 0.5 wt. % Cualloys processed with 2, 4 and 8 passes of route D, (in FIG. 5)respectively;

FIG. 5 is a graph showing the effect of number of passes and route ontexture intensity after ECAE of Al with 0.5 wt. % Cu;

FIG. 6 is a graph showing the effects of annealing temperature for routeA after ECAE of Al with 0.5 wt. % Cu;

FIG. 7 is a graph showing the effects of annealing temperature ontexture intensity for route B after ECAE of Al with 0.5 wt. % Cu;

FIG. 8 is a graph showing the effects of annealing temperature ontexture intensity for route C after ECAE of Al with 0.5 wt. % Cu;

FIG. 9 is a graph showing the effects of annealing temperature ontexture intensity for route D after ECAE of Al with 0.5 wt. % Cu:

FIG. 10 is a pole figure illustrating the texture as a result of theprocess described; and

FIGS. 11, 11A and 11B are schematic diagrams of an apparatus for ECAE ofbillets for targets.

DETAILED DESCRIPTION

The invention contemplates a sputtering target having the followingcharacteristics:

-   -   substantially homogenous material composition at any location;    -   substantial absence of pores, voids, inclusions and other        casting defects;    -   substantial absence of precipitates;    -   grain size less than about 1 μm;    -   fine stable structure for sputtering applications;    -   substantially uniform structure and texture at any location;    -   high strength targets without a backing plate;    -   controllable textures from strong to middle, weak and close to        random;    -   controllable combination of grain size and texture;    -   large monolithic target size;    -   prolonged sputtering target life;    -   optimal gradient of structures through target thickness.        Targets possessing these characteristics are producible by the        processes described.

Because of high purity, cast ingot metallurgy is useful in most casesfor billet fabrication in target production. However, casting results ina very course dendritic structure with strong non-uniformity in thedistribution of constitutive elements and additions across the ingot andlarge crystallites. Moreover, high temperature and long-timehomogenizing cannot be applied in current processing methods because ofthe further increase of grains. One embodiment of the invention solvesthis problem by using homogenizing time and temperature sufficient forredistribution of macrosegregations and microsegregations followed byequal channel angular extrusion (ECAE) with a sufficient number ofpasses, preferably from 4 to 6, for grain refinement.

Another embodiment eliminates other casting defects such as voids,porosity, cavities and inclusions which cannot be optimally removed byhomogenizing and employs a hot forging operation. In currently knownmethods hot forging has a restricted application because reductions arelimited and are typically used at low temperature working for grainrefinement. Other processes do not solve that problem when slab ingotsof the same thickness as the billet for ECAE are used. In the presentinvention, the as-cast ingot has a large length-to-diameter ratio,preferably up to 2. During hot forging, the ingot thickness changes tothe thickness of the billet for ECAE. That provides large reductionswhich are sufficient for full healing and elimination of cast defects.

Still another embodiment of the invention is directed to precipitate-and particle-free targets. With currently known methods precipitate-freematerial may be prepared by solutionizing at the last processing step.However, in this case heating to solutionizing temperatures producesvery large grains. The present invention provides a method forfabricating precipitate-free and ultra-fine grained targets. Accordingto this embodiment of the invention, solutionizing is performed at atemperature and time necessary to dissolve all precipitates and particlebearing phases and is followed by quenching immediately before ECAE.Subsequent ECAE and annealing are performed at temperatures below agingtemperatures for corresponding material conditions.

A further embodiment of the invention is a special sequence ofhomogenizing, forging and solutionizing operations. As-cast ingots areheated and soaked at the temperature and for the length of timenecessary for homogenizing, then cooled to the starting forgingtemperature, then forged to the final thickness at the final forgingtemperature (which is above the solutionizing temperature) and quenchedfrom this temperature. By this embodiment all processing steps areperformed with one heating. This embodiment also includes anothercombination of processing steps without homogenizing: forging at atemperature of about the solutionizing temperature and quenchingimmediately after forging.

It is also possible in accordance with the invention to conduct agingafter solutionizing at the temperature and for the length of timenecessary to produce fine precipitates with an in average diameter ofless than 0.5 μm. These precipitates will promote the development offine and uniform grains during following steps of ECAE

An additional embodiment of the invention is a billet for ECAE afterforging. An as-cast cylindrical ingot of diameter do and length h_(o)(FIG. 1A) is forged into a disk of diameter D and thickness H (FIG. 1B).The thickness H corresponds to the thickness of the billet for ECAE.Then two segments are removed from two opposite sides of the forgedbillet such as by machining or sawing (FIG. 1C), to provide a dimensionA corresponding to a square billet for ECAE (FIG. 1D). ECAE is performedin direction “C” shown on FIG. 1C. After the first pass the billet has anear-square shape if the dimensions of the ECAE billet (A×A×H), thedimensions of the forged disk (D×H) and the dimensions of the cast ingot(d_(o)×h_(o))are related by the following formulae:D=1.18Ad_(o) ²h_(o)=1.39.A²H

The invention further contemplates the fabrication of targets with fineand uniform grain structure. ECAE is performed at a temperature belowthe temperature of static recrystallization with the number of passesand processing route adjusted to provide dynamic recrystallizationduring ECAE. Processing temperature and speed are, correspondingly,sufficiently high and sufficiently low to provide macro andmicro-uniform plastic flow.

A method for fabricating fine and stable grain structures for sputteringapplications and to provide high strength targets is also provided. Thebillet after ECAE with dynamically recrystallized sub-micron structureis additionally annealed at the temperature which is equal to thetemperature of the target surface during steady sputtering. Therefore,the temperature of the target cannot exceed this sputtering temperatureand for structure to remain stable during target life. That structure isthe finest presently possible stable structure and provides the besttarget performance. It also provides a high strength target. FIG. 2shows the effect of the annealing temperature on the ultimate tensilestrength and yield stress of Al 0.5 wt. % Cu alloy after ECAE at roomtemperature with 6 or 4 passes. In both cases as-processed material hashigh strength not attainable for that material with known methods. Yieldstress is only slightly lower than ultimate tensile strength. Theincrease of the annealing temperature in a range from 125° C. to 175° C.that, it is believed, corresponds to possible variations of sputteringtemperature results in the gradual decrease of strength. However, evenin the worst case with an annealing temperature of 175° C. targetstrength and, especially, yield stress are much higher than the strengthof aluminum alloy AA6061 at T-O condition which is the most widely usedfor fabrication of backing plates (see FIG. 2). Thus, among otherthings, the invention provides the following significant advantages:

-   -   High strength monolithic targets may be fabricated from mild        materials like pure aluminum, copper, gold, platinum, nickel,        titanium and their alloys.    -   It is not necessary to use backing plates with additional and        complicated operations such as diffusion bonding or soldering.    -   Fabrication of large targets is not a problem.    -   Targets may easily be recycled after their sputtering life ends.

It is also useful to employ gradient annealing of targets after ECAE.For that purpose a preliminary machined target is exposed to the samethermal conditions as under sputtering conditions and kept at thoseconditions a sufficient time for annealing. FIG. 3 describes thatprocessing. The target 1 is fixed in a device 2 which simulatessputtering: a bottom surface A of the target is cooled by water while atop surface B is heated to the sputtering temperature. Heating isadvantageously developed at the thin surface layer by radiant energy q(left side of FIG. 3A) or inductor 3 (right side of FIG. 3A) In additionit is also possible to achieve gradient annealing of targets directly ina sputtering machine at the regular sputtering conditions beforestarting the production run. In all these cases distribution oftemperature through the target as shown in FIG. 3B through sections C—Cof FIG. 1 is non-uniform and annealing takes place only inside a verythin surface layer (δ). Following sputtering the same distribution ismaintained automatically. Thus, structural stability and high strengthof as-processed material are conserved for the main part of the target.

An additional embodiment comprises a two-step ECAE processing. At thefirst step ECAE is performed with a low number of passes, preferablyfrom 1 to 3, in different directions. Then, the preliminary processedbillet receives aging annealing at low enough temperatures but forsufficient time to produce very fine precipitates of average diameterless than about 0.1 μm. After intermediate annealing ECAE is repeatedwith the number of passes necessary to develop a dynamicallyrecrystallized structure with the desired fine and equiaxed grains.

It is also possible through use of the invention to control texture.Depending on the starting texture and the nature of the materials,various textures can be created. Four major parameters are important toobtain controlled textures:

-   -   Parameter 1: the number of repeated ECAE passes subjected to the        same work piece. This number determines the amount of plastic        deformation introduced at each pass. Varying the tool angle        between the two channels of the ECAE equipment enables the        amount of plastic straining to be controlled and determined and        therefore represents an additional opportunity for producing        specific textures. Practically, in most cases, a tool angle of        about 90° is used since an optimal deformation (true shear        strain ε=1.17) can be attained;    -   Parameter 2: the ECAE deformation route; that is defined by the        way the work piece is introduced through the die at each pass.        Depending on the ECAE route only a selected small number of        shear planes and directions are acting at each pass during        plastic straining.    -   Parameter 3: annealing treatment that comprises heating the work        piece under different conditions of time and temperature. Both        post-deformation annealing at the end of the ECAE extrusion and        intermediate annealing between selected ECAE passes are        effective ways to create various textures. Annealing causes the        activation of different metallurgical and physical mechanisms        such as second-phase particle growth and coalescence, recovery        and static recrystallization, which all affect more or less        markedly the microstructure and texture-of materials. Annealing        can also create precipitates or at least change the number and        size of those already present in the material: this is an        additional way to control textures.    -   Parameter 4: the original texture of the considered material.    -   Parameter 5: the number, size and overall distribution of        second-phase particles present inside the material.

With consideration of these five major parameters, control of texture ispossible in the ways described below:

Table 1 describes major components of texture between 1 and 8 ECAEpasses via routes A through D in the as deformed condition for a stronginitial texture and also for routes A and D for a weak initial texture.To describe major components both the 3 Euler angles (αβγ) according tothe Roe/Matthies convention and ideal representation {xyz} <uvw> areused. Moreover, the total volume percentage of the component is given.For texture strength both the OD index and Maximum of pole figures aregiven.

TABLE 1 Texture strength and orientation for route A as a function ofthe number of passes and initial texture Maximum Number Major TextureOrientations Notation: OD of Pole of Euler angles (αβγ):(xyz)<uvw>:%total index FIGS. passes N volume with 5° spread (t.r.) (t.r.) ROUTE A(STRONG INITIAL TEXTURE) Original (10.9 54.7 45):(−111)<1-23>:16% 21.717.02 (N = 0) (105 26.5 0):(−102)<−28-1>:14% (110 2426.5):(−215)<−5-5-1>:9.3% N = 1 (119 26.5 0):(−102)<−2-4-1>:17.62% 10.910.9 (346 43.3 45):(−223)<2-12>:7.62% N = 2 (138 26.50):(−102)<−2-2-1>:8.66% 6.1 6.9 (31 36.7 26.5):(−213)<−3-64>:8.6% N = 3(126.7 26.5 0):(−102)<−2-3-1>:7.45% 5.79 5.45 (21 36.726.5):(−213)<2-43>:6.1% N = 4 (26.5 36.7 26.5):(−213)<2-64>:9.42% 4.826.55 (138 26.5 0):(−102)<−2-2-1>:4.62% 169 15.8 45):(−115)<−32-1>:4.32%N = 6 (126.7 26.5 0):(−102)<−2-3-1>:6.66% 3.94 5.61 (228 33.70):(−203)<−34-2>:5.8% (31 36.7 26.5):(−213)<3-64>:3.42% N = 8 (0 35.245):(−112)<1-11>:3.1% 2.05 3.5 (180 19.4 45):(−114)<−22-1>:3.06% (3125.2 45):(−113)<1-52>:2.2% ROUTE A (WEAK INITIAL TEXTURE) Original (8025.2 45):(−113)<8-11 1>:4.3% 2.6 3.2 (N = 0) Large spreading around(106) (119) N = 1 (0 46.7 45):(−334)<2-23>:5.8% 4.02 6.3 (222 26.50):(−102)<−22-1>:5% (128 18.4 0):(−103)<−3-4-1>:4.01% N = 2 (126.7 26.50):(−102)<−2-3-1>:6.22% 4.4 6.8 (26.5 48.2 26.5):(−212)<1-22>:5.4% (16213.2 45):(−116)<−42-1>:5.4% N = 4 (226 36.7 26.5):(−213)<−12-1>:4.85% 35.1 (233 26.5 0):(−102)<−23-1>:4.63% (136 19.5 45):(−114)<−40-1>:4.54%(26.5 36.7 26.5):(−213)<2-64>:3.7% ROUTE B (STRONG INITIAL TEXTURE)Original (10.9 54.7 45):(−111)<1-23>:16.4% 21.7 17.02 (N = 0) (105 26.50):(−102)<−2-8-1>:14% (110 24 26.5):(−215)<−5-5-1>:9.3% N = 1 (119 26.50):(−102)<−2-4-1>:17.62% 10.9 10.9 (346 43 45):(−223)<2-12>:7.62% N = 2(0 48 26.5):(−212)<425>P24.24% 17.27 14.02 (216 15.845):(−115)<−24-1>:8.07% (138 26.5 0):(−102)<−2-2-1>:5.04% N = 3 (260 3674):(−2 7 10)<94-1>:15.49% 7.3 9.1 (118 18.4 90):(013)<−63-1>:5.23% N =4 (96 36 16):(−7 2 10)<−6-15-1>:12% 6 9.77 (187 15.626.5):(−21-8)<−32-1>:8.05% N = 6 (230.5 14 0):(−104)<−45-1>:12.46% 6.38.45 (100 36 16):(−7 2 10)<−4-9-1>:10.2% N = 8 (230.5 140):(−104)<−45-1>:9.19% 4.9 6.99 (180 13.2 45):(−116)<−33-1>:8.21% (10036 16):(−7 2 10)<−4-9-1>:7.48% ROUTE C (STRONG INITIAL TEXTURE) Original(10.9 54.7 45):(−111)<1-23>:16.4% 21.7 17.02 (N = 0) (105 26.50):(−102)<−2-8-1>:14% (110 24 26.5):(−215)<−5-5-1>:9.3% N = 1 (119 26.50):(−102)<−2-4-1>:17.62% 10.9 10.9 (346 43 45):(−223)<2-12>:7.62% N = 2(0 34.5 14):(−416)<4-13>:43.3% 48.9 25.9 (221.8 265 0):(−102)<−2 2−1>:10.5% N = 3 (254 148.4 0):(−103)<−3 11 −1>:7.5% 5.2 6.05 (111.5 46.518.4):(−313)<−2-3-1>: 6.6% N = 4 (130 36.9 10):(−304)<−4-6-3>:15.05%7.95 13.3 N = 5 Large spreading 2.4 3.3 (270 14 0):(−104)<010>:4.66%(26.5 48 26.5):(−212)<1-22>:2.54% N = 6 (110 36 16):(−7 210)<−5-8-2>:11.6% 6.32 9.3 (234 33.7 0):(−203)<−35-2>:5.7% N = 7 Largespreading 2.35 3.15 (242 18.4 0):(−103)<−36-1>:4.66% (188 11.445):(−117)<−34-1>:3.36% N = 8 (136.5 18.4 0):(−103)<−331>:14.71% 12.9 11(257 45 0):(−101)<−8 49 −8>:8.75% ROUTE D (STRONG INITIAL TEXTURE)Original (10.9 54.7 45):(−111)<1-23>:16.4% 21.7 17.02 (N = 0) (105 26.50):(−102)<−2-8-1>:14% (110 24 26.5):(−215)<−5-5-1>:9.3% N = 1 (119 26.50):(−102)<−2-4-1>:17.62% 10.9 10.9 (346 43 45):(−223)<2-12>:7.62% N = 2(0 48 26.5):(−212)<425>:24.24% 17.27 14.02 (216 15.8 45):(−115)<−2 4−1>:8.07% (138 26.5 0):(−102)(−2-2-1>:5.04% N = 3 (197 20.426.5):(−216)<−22-1>:9.57% 3.91 6.67 all other components < 3% ROUTE D(STRONG INITIAL TEXTURE) N = 4 (222 26.5 0):(−102)<−22-1>:13.34% 6.3467.36 all other components < 3.8% N = 6 (223.5 18.5 0):(−103)<−33-1>:7.4%2.72 4.26 all other components < 2.5% N = 8 (222 26.50):(−102)<−22-1>:3.42% 1.9 3.01 all other components < 3% ROUTE D (WEAKINITIAL TEXTURE) Original (80 25.2 45):(−113)<−8 −11 1>:4.3% 2.6 3.2 (N= 0) Large spreading around (106) (119) N = 1 (0 46.745):(−334)<2-23>:5.8% 4.02 6.3 (221 26.5 0):(−102)<−22-1>:5% (128 18.40):(−103)<−3-4-1>:4.01% N = 2 (241 26.5 0):(−102)<−24-1>:12.72% 5 6.7(26.5 48.2 26.5):(−212)<1-22>:4.1% N = 3 (197 20.˜26.5):(−216)<−22-1>:8.8% 3.5 6.44 (26.5 48.2 26.5):(−212)<1-22>:3.9% N =4 (221.8 26.5 0):(−102)<−22-1>:7.2% 3 5.3 (26.5 48.226.5):(−212)<1-22>:3.1%

Table 2 describes major components of features between 1 and 8 ECAEpasses via route A through D for a strong initial texture and afterannealing at (150C, 1h), (225C, 1h) and (300C, 1h)

TABLE 2 Major texture orientations for route A in function of number ofpasses N and annealing temperature Notations: Euler angles (αβγ): (xyz)<uvw>: % total volume with 5° spread Annealing Annealing at (225C,Annealing at (300C, N at (150C, 1 h) 1 h) 1 h) ROUTE A (STRONG INITIALTEXTURE) 1 (43 47 22):(−525)<1- (35 48 25):(−212)<1- (76 29.5 45):(−225)32>:10.4% 22>:13.15% <−5-71>:9.3% (110 26.5 0):(−102)< (114 2210):(−102)< (141 37 0):(−304)< −2-6-1>:8.04% −2-4-1>:9.3% −4-4-3>:6.6%(130 24 18.4):(−317)< −3-2-1>:7.15% 2 (105 22 0):(−205)<−5 (136 18.40):(−103)< (354 18.4 0): 20-2>:9.21% −3-3-1>:20.9% (−103)<913>:7.74%(155 19.5 45):(−114)< (112 19 18.4): (315 11.5 45): −31-1>:7.83%(−319)<−5-6-1>: (−117)<701>:7.38% (31 36.7 45):(−213)<3- 20.2% (90 70):(−108)<0- 64>:6.88% 10>:6.7% 3 (110 36 16):(−7 2 10)< (110 450):(−101)< Large spreading −4-9-2>: 15.2% −1-4-1>:16.85% around (117),(100) (233 26.5 0):(−102)< (290 45 0): All −23-1>:7.35%(−101)<141>:11.5% components < 4% 4 (129 18 26):(−217)< (124 2514):(−419)< (110 25.2 45): −1-5-1>:11.73% −3-3-1>:12.4% (−113)<−6-3-1>:(35 37 26.5):(−213)<2- (38 36.7 26.5): 6.87% (318 25.2 53>:11.2%(−213)<3-95>:7.5% 45):(−113)<301>: 5.1% 6 (180 19.5 45):(−114)< Largespreading (46.7 19.5 45): −22-1>:5.5% All components < 5% (−114)<−1-17(135 10 0):(−106)<−6- 4>:9% 6-1>:4% All (0 46.7 45):(−334)<2- components< 4.9% 23>:3.95% 8 Large spreading (44 36 26.5): (152 32 0):(−508)<around (315), (−213)<2-63>:7.94% −8-5-5>:6.4% (104) (136 18.4 0):(−103)<All components < All components < 4% −3-3-1>:6.17% 3% ROUTE B (STRONGINITIAL TEXTURE) 1 (43 47 22):(−525)<1- (35 48 25):(−212)<1- (76 29.545):(−225) 32>:10.4% 22>:13.15% <−5-71>:9.3% (110 26.5 0):(−102)< (11422 10):(−102)< (141 37 0):(−304)< −2-6-1>:8.04% −2-4-1>:9.3%−4-4-3>:6.6% (130 24 18.4):(−317)< −3-2-1>:7.15% 2 (215 20 26.5):(−216)<(112 34 0):(−203)<−3- (221 26.5 0):(−102) −36-2>:35% 9-2>:16%<−22-1>:13.3% (270 13.2 45): (16 54.7 45):(−111)<1- (109 14 0):(−104)<(−116)<110>: 34>:8.88% −4-12-1>:12% 16% 3 (148 19 79):(−1 5 15)< (10 4510):(−616)<3- (0 48 26.5):(−212)< −55-2>:17.5% 13>:5.7% 4-25>:6% (90 1645):(−115)<−1- (235 14 0):(−104)<46- (222 41 45): 10)>: 1>:4.53%(−223)<03-2>:5.8% 6.9% Large spreading (19.5 45 0): (−101)<2-12>:5.4% 4(127 26.5 0):(−102)< (230 14 0):(−104)< Large spreading −2-3-1>:5.9%−45-1>:6.23% around (107) (115) (242 14 0):(−104)<−4 All components <8-1>: 3% 6 (180 19.5 45):(−114)< Large spreading (46.7 19.5 45):−22-1>:5.5% All components < 5% (−114)<−1-17 4> (135 10 0):(−106)<−6-:9% All 6-1>:4 components < 4.9% (0 46.7 45):(−334)<2- 23>:3.95% 8 Largespreading (44 36 26.5):(−213)<2- (153 32 0):(−508)< around (315), (104)63>:7.94% −8-5-5>:6.4% All components < 4% (136 18.4 0):(−103)< Allcomponents < −3-3-1>:6.17% 3% ROUTE C (STRONG INITIAL TEXTURE) 1 (43 4722):(−525)<1- (35 48 25):(−212)<1- (76 29.5 45):(−225) 32>:10.4%22>:13.15% <−5-71>:9.3% (110 26.5 0):(−102)< (114 22 10):(−102)< (141 370):(−304)< −2-6-1>:8.04% −2-4-1>:9.3% −4-4-3>:6.6% (130 24 18.4):(−317)<−3-2-1>:7.15% 2 (191 16 45):(−115)< (99 46 14):(−414)<−3- Largespreading −23-1>:8.77% 8-1>:20.9% around (100) (156 26.5 0):(−102)< (28945 0):(−101)<141 All components < −2-1-1>:6.68% >:15.22% 3.8% 3 (11926.5 0):(−102)< (106 29 26.5):(−214)< (194 14 0):(−104)< −2-4-1>:28.4%−5-6-1>:19.5% −41-1>:6.1% (26.5 48 26.5):(−212)< (103 31 34):(−326)<(163 18.4 0):(−103) 1-22>:9.74% −6-6-1>:18.7% <−3-1-1>:5.85% (42 46.518.4):(−313) <1-32>:8.83% 4 105 38 18.5):(−314)< Large spreading Largespreading −3-5-1>:10.2% around (302) and (225) around (100) (105) OtherAll (116) components < 5.3% components < 2.8% All components < 4.1% 5(103 32 18.4):(−315)< (127 26.5 0):(−102)< Large spreading −4-7-1>:19%−2-3-1>:7% around (106) (115) (22 38 18.4):(−314)<1- All components <11>:5.6% 3.7% 6 (61 46 14):(−414)<1- Large spreading (80 25 45):(−113)<83):11.82% around (101) and (334) −8-11 1>:4.3% (155 21 18.4):(−318)<All components < 4% All components < −22-1>:7.94% 3% 7 (104 36 16):(−7 210)< (125 37 0):(−304)< Large spreading −3-6-1>:29% −47-3>:7.8% around(100) (105) (26.5 48 26.5):(−212)< (305 45 0):(−101)< (203) 1-22>:7.6%121>:5.82% All components < 2.9% 8 (104 47 22):(−525)< (106 3818.4):(−314)< Large spreading −3-5-1>:15.36% −3-5-1>4.64% around (100)(105) All (112) (203) components < 3.2% All components < 2.7% ROUTE D(STRONG INITIAL TEXTURE) 1 (43 47 22):(−525)<1- (35 48 25):(−212)<1- (7629.5 45):(−225) 32>:10.4% 22>:13.15% <−5-71>:9.3% (110 26.5 0):(−102)<(114 22 10):(−102)< (141 37 0):(−304)< −2-6-1>:8.04% −2-4-1>:9.3%−4-4-3>:6.6% (130 24 18.4):(−317)< −3-2-1>:7.15% 2 (215 21 26.5):(−216)<(112 34 0):(−203)< (222 26.5 0):(−102) −36-2>:35% −3-9-2>:16.45%<−22-1>:13.3% (270 13 45):(−116)< (16 54.7 45):(−111)<1- (109 140):(−104)< 110>:16% 34>:8.88% −4-12-1>:12% (162 9 45):(−119)<−63-1>:9.6% 3 (337 50 34): (168 20 25):(−216)< (150 16 45):(−323)<101>:12.2% −82-3>:10.35% (−115)<115)<−41-1 (215 47 45):(−334)<0(102 18.4 0):(−103)< >:5.6% (198 18.4 4-3>:9.75% −3-16-1>:9.32%0):(−103)<−31-1>: (241 26.5 0):(−102)< (162 13 45):(−116)< 5.2%−24-1>:7.02% −42-1>:6.44% 4 (233 26.5 0):(−102)< Large spreading Largespreading −23-1>:9% All around (105) (116) All other components < 3.6%All components < components < 4% 3.9% 6 (224 18.4 0):(−103)< (224 18.40):(−103)< Large spreading −33-1>:8.29% −33-1>:5.49% around (106) andAll other components (109 18.4 0):(−103)< (113) <3.8% −3-9-1>:4.4% Allcomponents < 2.9% 8 (222 27 0):(−102)< (205 21 18.4):(−138)< (222 26.50):(−102) −22-1>:8.58% −22-1>:11.44% <−22-1>:8.58% All components < 4%(233 26.5 0):(−102)< (38 16 45):(−115)< −23-1>:10.74% 1-92>:5.55%

(1) The number of ECAE passes permits the control of texture strength.The increase of the number of passes is an efficient mechanism ofrandomizing texture. There is an overall decrease of texture strengthevidenced by the creation of new orientations and, more importantly, thelarge spreading of orientations around the major components of thetexture as evidenced in FIG. 4. FIG. 4 is an illustration of (200) polefigures for Al with 0.5 wt. % Cu alloys processed 2, 4 and 8 passes ofroute D (FIG. 5) and shows spreading of orientations as “N” increases.This phenomenon is more or less effective depending on the investigatedroute and/or annealing treatment. For example in the as-deformed state,routes B and C result in somewhat higher textures than routes A and D(FIG. 5 and Table 1). FIG. 5 is a graph that shows the influence of ECAEdeformation route and strength on texture formation as a function ofnumber of ECAE passes. For medium to very strong starting textures, twomain areas can be distinguished in the as-deformed state (FIG. 5):

Between passes 1 and 4 (with a tool angle of 90°), very strong to mediumtextures are obtained. In the investigation of Al.5Cu, for example, theOD index ranges from more than 7 times random to more than 48 timesrandom which corresponds to maximum intensities of the ODF between 3000mrd (30 times random) and more than 20000 mrd (200 times random).

For more than 4 passes (with a tool angle of 90°), medium-strong to veryweak textures close to random are created. In the case of A1.5Cu alloys,OD index varies from around 11 times random to less than 1.9 timesrandom depending on the route, which corresponds to maximum intensitiesof the ODF between 7000 mrd (70 times random) and around 800 mrd (8times random).

The two main domains are maintained after subsequent annealing, as shownin the graphs of FIGS. 6, 7, 8 and 9. However for some ECAE deformationroutes (for example route B and C in the case of A1.5Cu), additionalheating can give a strong texture, as discussed below. The existence ofthese two areas is a direct consequence of the microstructural changesoccurring in the material during intensive plastic deformation. Severaltypes of defects (dislocations, microbands, shear bands and cells andsub-grains inside these shear bands) are gradually created during the 3to 4 ECAE passes (for a tool angle of 90°). The internal structure ofmaterials is divided into different shear bands while increasing thenumber of passes. After 3 to 4 ECAE passes, a mechanism termed dynamicrecrystallization occurs and promotes the creation of sub-micron grainsin the structure. As the number of passes increases these grains becomemore and more equiaxed and their mutual local mis-orientations increasegiving rise to a higher number of high angle boundaries in thestructure. The very weak and close to random textures that are createdare a consequence of three major characteristics of the dynamicallyrecrystallized microstructures: the presence of high internal stressesat the grain boundaries, the large number of high angle boundaries andthe very fine grain size with a large grain boundary area (usually ofthe order of about 0.1-0.5 μm).

(2) The ECAE deformation route permits control of the major orientationsof the texture. Depending on the route, different shear planes anddirections are involved at each pass (see FIG. 5 and Tables 1 and 2).Therefore shear bands of different orientations are created in thestructure. For some routes these shear bands always intersect each otherin the same way; for other routes new families are constantly introducedat each pass (Tables 1 and 2). All these options allow changes to themajor components or orientations between each pass. The effect isparticularly strong for a small number of passes before the advent ofdynamic recrystallization, as discussed above. An important applicationexists in the possibility to create different types of strong texturesalready in the as deformed state for a limited number of ECAE passes.

(3) Additional annealing has an important influence on both the majortexture orientations and strength (see FIGS. 6, 7, 8, 9 and Table 2).

For annealing temperatures below the static recrystallization, a changein both texture strength and main orientation is observed. This effectcan be particularly strong for a low number of passes (less than about 4passes) leading to remarkable migrations of major orientationsaccompanied with either a decrease or increase of texture strength. Suchchanges can be attributed to the instability of microstructural defectswhich are implemented in the crystal structure. Complex mechanisms suchas recovery and sub-grain coalescence explain partly the observedphenomena. For dynamically recrystallized ultra-fine structure (afterusually 4 passes) smaller modifications are encountered. They areusually associated with the transition from a highly stressed to a moreequilibrium micro structure.

For annealing temperatures close to the beginning of staticrecrystallization, the same over-all results as in the above case arefound. However, it is important to note that new and different texturesthan for low temperature annealing can be obtained, especially for a lownumber of ECAE passes (Table 2). This is due to static recrystallizationwhich creates new grains with new orientations by diffusion mechanisms.

For annealing temperatures corresponding to developed stages of staticrecrystallization (full static recrystallization), textures tend to beweakened (as shown in FIGS. 6, 7, 8, 9 and Table 2). This isparticularly true after 3 or 4 ECAE passes where very weak and almostrandom textures are created. These textures are characterized by four,six or eight fold symmetry with a higher number of cube (<200>)components.

Additional textural analysis of ECAE deformed Al and 0.5 wt. % Cu isshown in the pole figure described in FIG. 10. In this case the samplewas given an initial thermochemical treatment of casting plushomogeneous plus hot forging plus cold rolling (˜10%) plus two ECAEpasses via route C plus annealing (250° C., 1 hour). The recrystallizedmicrostructure had grain size-of 40-60 μm and strong texture along{−111}<2-12>, {012}<−130>, {−133}<3-13>. The result shows two ECAEpasses (C) plus static recyrstalization permits removal of the verystrong (220) textural component of the as-forged condition.

By taking into account all the foregoing, results show that intermediateannealing between each pass provides several additional and significantopportunities to adjust desired textures. Two options are available:

-   -   A. Intermediate annealing either at low temperature or just at        the beginning of static recrystallization after a low number of        passes (N<4) can give strong textures with new orientations        after subsequent deformation with or without annealing.    -   B. Intermediate annealing in the case of full static        recrystallization after a low or high number of passes can lead        more easily to very weak textures after subsequent deformation        with or without annealing.

It is also possible to repeat intermediate annealing several times inorder to enhance the effects described above.

-   -   (4) Starting texture has also a strong influence on both texture        and strength especially after a limited number of passes        (usually after 1 to 4 passes). For a higher number of passes the        ECAE deformation is very large and new mechanisms are taking        place which lessen the magnitude of the influence of the        starting texture. Two situations are noted (FIG. 5 and Table 1        for route A and D):    -   A. For a strong to medium starting textures, after further        deformation with or without annealing, it is possible to obtain        very strong to medium textures before 4 passes and strong-medium        to very weak textures after approximately 4 passes according to        the results described in paragraph 1, 2 and 3.    -   B. For medium to very weak starting textures it will be more        difficult to obtain very strong to strong textures at least in        the as-deformed state. Weak starting textures are more likely to        enhance and promote weak to random textures after ECAE        deformation with or without annealing (Table 1).

(5) Second phase particles have a pronounced effect on texture. Large(>1 μm) and non-uniformly distributed particles are not desired becausethey generate many problems such as arcing during sputtering. Very fine(>1 μm) and uniformly distributed second phase particles are ofparticular interest and offer many advantages. Firstly, they tend tocreate a more even stress-strain state during ECAE deformation.Secondly, they stabilize the already ECAE-deformed microstructure inparticular after further annealing. In this case particles pin grainboundaries making them more difficult to change. These two major effectsevidently affect the texture of materials. Especially:

-   -   for a small number of passes (<4 passes), the effects described        previously in sections (1) to (4) can be enhanced due to the        presence of second phase particles in particular for strong        textures.    -   for a large number of passes, second phase particles are        effective in promoting the randomization of texture.

In order to take advantage of the possibilities offered by the ECAEtechnique in terms of texture control, three types of results can beachieved:

-   -   A. Materials (sputtering targets) with strong to very strong        (ODF>10000 mrd) textures. In particular this can be obtained for        a small number of passes with or without subsequent annealing or        intermediate annealing. A strong starting texture is a factor        favoring the creation of strong textures. For example in the        case of A1.5Cu alloy Table 1 gives all the major components of        orientations which were created for different deformation routes        (A,B,C,D) between 1 and 4 passes. The as-deformed state as well        as deformation followed either by low temperature annealing        (150° C., 1h) or by annealing at the beginning of static        recrystallization (225° C., 1h) or after full recrystallization        (300° C., 1h) are considered in this table. The original texture        is a displayed in FIG. 7. It is important to note that in most        cases new types of textures have been found. Not only (200) and        {220} textures are present but also {111}, {140}, {120}, {130},        {123}, {133}, {252} or, for example, {146}. For strong textures,        one or two main components are usually present.    -   B. Material (sputtering targets) with weak to close to random        textures with an ultra-fine grain size less than 1 μm. Whatever        the route this can be obtained after more than 3 to 4 ECAE        passes followed or not by annealing or intermediate annealing at        a temperature below the beginning of recrystallization        temperature. A very weak starting texture is a factor favoring        the creation of close to random textures.    -   C. Statically recrystallized materials (sputtering targets) with        weak to close to random textures with a fine grain size above        approximately 1 μm. Whatever the route this can be obtained        after more than 3 to 4 ECAE passes followed by annealing or        intermediate annealing at a temperature above the beginning of        recrystallization temperature. A very weak starting texture is a        factor favoring the creation of close to random textures.

Another embodiment of the invention is an apparatus for performing theprocess to produce targets. The apparatus (FIGS. 11, 11A and 11B)includes die assembly 1, die base 2, slider 3, punch assembly 4, 6hydraulic cylinder 5, sensor 7, and guide pins 11. Also the die isprovided with heating elements 12. Die assembly 1 has a vertical channel8. A horizontal channel 9 is formed between die assembly 1 and slider 3.The die is fixed at table 10 of press, punch assembly 4, 6 is attachedto press ram. In the original position a—a the forward end of slider 3overlaps channel 1, punch 4 is in a top position, and a well lubricatedbillet is inserted into the vertical channel. During a working strokepunch 4 moves down, enters channel 8, touches the billet and extrudes itinto channel 9. Slider 3 moves together with billet. At the end ofstroke the punch reaches the top edge of channel 9 and then returns tothe original position. Cylinder 5 moves the slider to position b—b,releases the billet, returns the slider to the position a—a and ejectsthe processed billet from the die. The following features are noted:

-   -   (a) During extrusion slider 3 is moved by hydraulic cylinder 5        with the same speed as extruded material inside channel 9. To        control speed, the slider is provided with sensor 7. That        results in full elimination of friction and material sticking to        the slider, in lower press load and effective ECAE;    -   (b) Die assembly 1 is attached to die base 2 by guide pins 11        which provide free run δ. During extrusion the die assembly is        nestled to the base plate 2 by friction acted inside channel 8.        When the punch returns to the original position, no force acts        on the die assembly and slider, and cylinder 3 can easily move        the slider to position b—b and then eject the billet from the        die.    -   (c) Three billet walls in the second channel are formed by the        slider (FIG. 11A) that minimizes friction in the second channel.    -   (d) The side walls of the second channel in the slider are        provided with drafts from 5° to 12°. In this way the billet is        kept inside the slider during extrusion but may be ejected from        the slider after completing extrusion. Also, thin flash formed        in clearances between the slider and die assembly may be easily        trimmed.    -   (e) Die assembly is provided with heater 12 and springs 13.        Before processing, springs 13 guarantee the clearance 6 between        die assembly 1 and die base 2. During heating this clearance        provides thermoisolation between die assembly and die base that        results in short heating time, low heating power and high        heating temperature.

The apparatus is relatively simple, reliable and may be used withordinary presses.

1. A sputtering target formed from a cast material and comprising: a yield strength of greater than 50 mega Pascal (MP), and an ultimate tensile strength of greater than 125 MP; a substantial absence of pores, voids and inclusions; and an average grain size of less than about 1 μm, the target having an annealed upper surface portion and a remaining portion that is un-annealed.
 2. The sputtering target of claim 1 comprising one or more of Al, Ti, Cu, Ta, Ni, Mo, Au, Ag, and Pt.
 3. The sputtering target of claim 1 comprising an alloy which includes at least one of Al, Ti, Cu, Ta, Ni, Mo, Au, Ag and Pt.
 4. The sputtering target of claim 1 further comprising a substantial absence of precipitates.
 5. The sputtering target of claim 1 further comprising a substantially uniform structure and texture at any location.
 6. The sputtering target of claim 1 further comprising a substantially homogeneous composition at any location.
 7. The sputtering target of claim 1 wherein both the yield strength and the ultimate tensile strength are greater than 125 MP.
 8. The sputtering target of claim 1 wherein both the yield strength and the ultimate tensile strength are greater than 150 MP. 